[BC] Re: Long serial connections

[Broadcast List USER]

One of the many advantages of RS-422 is that it can be extended much  
further.

AND the RS-232 standard IS 50 feet, unless you use low capacitance  
cable, assuming maximum data rate.

The 50 feet is based on a total capacitance of 2500 pF, which is the  
actual limiting factor.  If you use low capacitance cable, the  
distance can be extended.  As an example, if you use CAT-5 cable, the  
lower capacitance allows the maximum distance to be extended to 147  
feet.

Also, since the capacitance "rounds off" the edges of the data  
transitions, you can slow down and still have a system that works.   
This is NOT part of the EIA232 standard, but it works in practice.

Texas Instruments, who makes a lot of the UART and line driver chips  
in use, has published this data:
Baud rate		Maximum cable length (ft)
19200		50
9600		500
4800		1000
2400		3000

Then there is the odd thing that some users have pushed the maximum  
speed, WELL beyond the standard, up to 200,000 BAUDS.

--chip

On Mar 8, 2009, at 3:13 PM, broadcast-request at radiolists.net wrote:

> Message: 11
> From: Sam Roffe <sam.roffe at gmail.com>
>
> I'm running a RS422 circuit that is about 600 feet long, and running
> through a couple punch down blocks to.  Seems to be solid as a rock.
>
> On Sun, Mar 8, 2009 at 6:40 AM, Craig Bowman <craig1 at shianet.org>  
> wrote:
>> First of all, never believe anything Wikipedia has written on its
>> pages.  Secondly, 1,000 feet is the number.  I have run serial
>> connections well over 200' using 8451 with no problem.  I have  
>> also used
>> three conductors on multi-pair between studios and the rack room on a
>> different floor with no problem which involved a couple hundred  
>> feet of
>> wire and four 66 block connections.
>>
>> Craig Bowman
>
> -- 
> Sam Roffe